In each case of MCPyV-pseudonegative (MCC UK11) or -pseudopositive (MCC64) MCC determined by CM2B4 IHC, nuclear ST-1 imunoreactivity corresponded to the data of real-time PCR for LT-DNA, conventional PCR for ST-DNA, and real-time PCR or ISH for ST mRNA. The gene discussed is SDCBP; the disease is Merkel cell skin cancer.